Duct jointing system

ABSTRACT

A means for connecting together sheet metal ducts, e.g. forced air heating ducts, in end-to-end relationship, comprises hollow, roll formed flange members which extend along the edges of adjacent duct ends, and L-shaped corner pieces the limbs of which can be inserted into the ends of the flange members to complete the joint at the corners. A sealing agent or gasket is located between sets of flange members and corner pieces. The flange members have planar side end surfaces for sealing reception of the gasket, and lower protuberances, into which the ends of the metal ducts fit, the protuberances being arranged to bite into the gasket to improve the seal. The corner pieces have laterally offset portions, allowing the raw edge of the duct, at the corners, to project forwardly of the side surface of the corner piece, and hence to bite into the gasket at the corners to improve the seal. Channel shaped cleats are provided to assist in the attachment of pairs of profiles on adjacent end arranged ducts. Bolt holes are provided through the corner pieces for the primary attachment means.

FIELD OF THE INVENTION

This invention relates to a means and apparatus for connecting together sheet metal ducts in end-to-end relationship, for use with medium and high pressure and larger low pressure fluid flow systems.

BACKGROUND OF THE INVENTION

In the construction of buildings and installation of forced air heating and air conditioning systems, as well as in other applications such as solar heating arrangements, it is necessary to install and connect together sections of sheet metal ducts to form long, continuous conduits through which fluids, namely hot or cold air, may be conducted. Normally such ducts are rectangular in section, for ease of installation and economy of space. Their end-to-end jointing, of straight sections, curved sections, elbows, corners or the like, poses problems, however. To provide some form of interfitting connecting apparatus considerably increases the expense of manufacture of the sections and particularly installation costs. It is desirable that leakage of air at the joints be minimized. Also, the joints should consist of simple, economical components which can be readily and simply used and installed on the duct, either in the shop or on the site. Permanent jointing as by welding is undesirable, since it renders maintenance and replacement of individual sections difficult and is very costly. At the same time the joints must be durable and long lasting, able to withstand the conditions of use (exposure to heated or cooled air flows for periods of many years) in a building for extended periods of time.

BRIEF DESCRIPTION OF THE PRIOR ART

Previous proposals to meet this problem have used simple sheet metal cleats such as standing S-cleats, standing T-cleats etc., welded angle iron framework jointing systems, namely companion angle flanges, in which the ends of adjacent duct sections are provided with frames or flanges extending laterally outwardly from the duct sections. Then these frame pieces can be bolted or otherwise secured together in face-to-face relationship, to join the duct sections. Sealing gaskets or compounds can be provided between these frames attached to respective sections, to form a sealed joint along most of the connection length. In most of the aforementioned systems the effectiveness of the seal relies solely on the generous application of caulking which by nature is so unreliable that air losses in the order of 10% are common. In many common systems, the flanges are formed by notching and then bending back end areas of the ducts themselves, which is an imprecise yet costly method and leads to leakage.

For corner jointing arrangements, it has been proposed to make the frames extending along the duct section walls hollow and open-ended, and then to provide L-shaped corner pieces for insertion into the ends thereof. Then these corner pieces can be clamped or bolted together in face-to-face relationship also, to complete the jointing of the sections. General arrangements of this nature are to be found disclosed in U.S. Pat. No. 3,199,901 Jeppson; U.S. Pat. No. 3,428,324 Chambers; U.S. Pat. No. 565,499 Pattison.

All of the previously proposed arrangements have, however, suffered from one or more disadvantages, notably in connection with the degree of sealing. Without careful and proper arrangements of the design of the various interconnecting parts, so that they can be properly assembled in a close, sealing manner, allowing provision for additional, and in many cases complex and time consuming, sealing means were necessary, a joint sealed to protect against excess leakage of air flows from the duct joint is not achieved.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a novel form of duct connecting means of the above-described general type.

The present invention provides a duct connecting means which utilizes a combination of hollow elongated roll-formed flange members which extend along the major portion of the four wall edges of a duct, and generally planar L-shaped corner connecting pieces the limbs of which can be inserted into and co-operate with the ends of the flange members to complete the joint. Both the flange members and the L-shaped corner connecting pieces are shaped and designed as to their configuration and dimensions so as to enhance the overall sealing efficiency of the joint when in full assembly. Briefly, the flange members each have channel portions in which the end walls of the duct sections are received, and upstanding planar end walls. The channels, however, are arranged to allow the duct section to extend forwardly into a position substantially flush with the end planar wall of the upstanding section of the flange members. This entails the provision of a protruberance at the bottom of the upstanding flange, which contacts the corresponding protruberance on the flange member on the end adjacent section in the assembled joint. At their centres, the L-shaped corner connecting pieces are each provided with planar offset portions, one of which forms a continuous planar wall with the upstanding planar end face of the flange member, and the other of which, offset in the opposite direction, forms with its opposite number on the edge adjacent duct section, well defined side walls of a cavity for receiving the gasket corner portion therein, whilst allowing the duct section corner edges to protrude beyond the corner piece surface, to bite into and form a corner seal with the gasket.

Thus, according to the present invention, there is provided a connection means for connecting adjacent ends of rectangular sheet metal ducts, comprising:

a plurality of elongated hollow flange members each having a channel portion with a mouth opening to receive therein an end face of a wall of said sheet metal duct and to extend along a major art of the length thereof, and a transverse hollow portion upstanding from the channel portion, said transverse portion having a generally planar upstanding outer side face;

the channel portion extending beyond the plane of said outer face so that the end face of a duct received therein may lie substantially flush with said outer side face;

the transverse portion having openings at each longitudinal end thereof;

a substantially planar, generally L-shaped corner connecting piece, the limbs thereof being adapted to be received in the openings in the longitudinal ends of adjacent ones of said hollow flange members so as to link a pair of flange members together in mutually right angular disposed relationship with planar outer side faces substantially in a common plane;

said corner connecting piece having a first laterally offset portion at its radially inner central corner section and a second laterally offset portion at its radially outer central corner section, the first and second offset portions being offset in opposite directions from one another;

said corner connecting piece being adapted to be assembled with a pair of said flange members with said first laterally offset portion being offset in the direction away from the planar outer side faces thereof.

Thus, the arrangement according to the present invention enables substantially complete sealing of the joint between end adjacent sheet metal duct sections to be achieved. The corner pieces are designed in co-operation with the shape of the flange member, so as to provide continuous planar surfaces around the corners of the joint for reception therein of a gasket in proper sealing relationship. The first offset portion of the L-shaped corner connecting piece referred to above, forms a cavity at the corner of the duct, along with its opposite number on the end adjacent duct section, into which the opposed corner edges of the duct sections protrude, towards, each other, beyond the surfaces of the opposed first offset portions. The duct edges can thus bite into the sealing gasket in the cavity at the corners, to provide full sealing of the duct joint at the corners thereof.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In a preferred embodiment of the invention, the corner connecting pieces have a lip or flanged portion along their outer edges, extending in the direction of the offset of the first and said offset portion. The hollow flange members are also suitably shaped at their outer edges to receive the flanged portion of the corner pieces, for better co-operation and interference fitting of the parts on assembly. Also, the duct sections may be an interference fit into the channels of the hollow flange members, so that these can be fitted into place, until the ends of the duct walls engage against the forward most wall of the channel section of said hollow flange members. Then their securing can be completed e.g. by means of sheet metal screws or spot welding, or by application of suitable adhesive. Securing cleats may be provided, of channel section, to fit over juxtaposed flange members and corner piece flanges, to assist in securing all members in the assembled joint.

In another preferred feature of the invention, bolt holes are provided adjacent the corners of the L-shaped corner connecting pieces, so that the corner connecting pieces when assembled on adjacent sheet metal duct sections can be bolted together to complete the connection. Preferably also, the bolt hole has a section to engage a shoulder on a bolt and prevent its rotation, for ease of installation in relatively inaccessible positions. Preferably also, the shank of the bolt which is installed through the bolt holes of the L-shaped corner connecting pieces has a non-threaded portion on its shank corresponding in length to the separation between the installed corner connecting pieces and the thickness thereof, so as to prevent overtightening of a nut applied to the bolt, and thereby avoid distortion of the parts after assembly, with possible deterioration of the seal.

BRIEF REFERENCE TO THE DRAWINGS

FIG. 1 is a general perspective view of two duct sections with connection means according to the invention, arranged ready for connection in end-to-end relationship;

FIG. 2 is a fragmentary perspective view of parts of a duct connection means according to the invention;

FIG. 3 is a sectional view along the line 3--3 of FIG. 1;

FIG. 4 is a sectional view along the line 4--4 of FIG. 1;

FIG. 5 is a perspective view of part of a connection means as in FIG. 1, in partially assembled condition;

FIG. 6 is a perspective view of a corner connecting piece and flange member ends assembled therewith.

In the drawings, like reference numerals indicate like parts.

DETAILED DESCRIPTION OF THE SPECIFIC PREFERRED EMBODIMENT

The duct connection means as illustrated comprises a plurality of elongated hollow flange members such as 10, one such flange member being provided for the end of each side wall 12 of a rectangular section sheet metal duct 14 of a forced air system. Thus, as shown in FIG. 1, two essentially similar duct sections in end-to-end relationship are fitted on all four sides with flange members 10 ready for connection together. Between the longitudinal ends of adjacent flange members 10 on one duct section 14 are provided corner connecting pieces 26. A sealing gasket 17 is provided, to fit between the end faces of opposed sets of flange members 10 and corner connecting pieces 16.

As shown in more detail in FIG. 2, each flange member 10 has a channel portion 16 and a transverse hollow portion 18, upstanding from the channel portion 16. The outer side face 20 of the upstanding portion 18 is generally planar.

The channel portion 16 extends beyond the plane of the outer face 20 of the upstanding portion 18, to terminate in a nose-like protruberance 22 into the interior of which a sealing compound 29 has been deposited (FIGS. 2 and 3). The channel member 16 thus accommodates the side wall 12 of the duct 14 received therein, to engage against the inner wall of protuberance 22 and form a stop means for the edge 24 of the side wall 12 of the duct, in substantial alignment with the smooth, planar side surface 20 of the upstanding portion 18 of the profile member 10. At its other end, the channel section 16 has a mouth 23, through which the side wall 12 can be inserted. Thus, the profile 10 can be positioned onto the side wall 12 until the edge 24 engages the inner wall of protuberance 22, and then the side wall is in correct relationship. The flange members 10 are attached to the ducts 14 by means of sheet metal screws 25. The profile is a hollow member, readily made by extrusion or roll forming, into the desired shape. The profiles 10 have a length which is less than the width of the duct walls 12, so that the sides of the duct walls extend a short way beyond the end of the profiles 10. When the two duct sections 14 with attached profiles 10 are placed in end-to-end relationship joining together, the protuberances 22 on opposed profiles define the narrowest part of the gap, along their full length. Thus an elongated planar sided pocket is formed, defined by planar side wall faces 20, for even reception and mounting of the sealing gasket 17. The protuberances 22 bite into the gasket 17 opposite the duct edges 24, to enhance the sealing of the joint. The metal walls of the profile 10 are of substantially constant thickness, so that the edges 24 of the opposed duct section 14 are separated from one another, in the assembled structure, by a distance of approximately two metal wall thicknesses. Mastic material 29 is provided inside the protuberances 22, to improve the seal of the duct edges 24 therein, and avoid leakage of air from the interior of the ducts out of channel portion 16.

L-shaped corner connecting pieces such as 26 are provided, one for each flange member 10. Each corner piece has similar first and second limbs 28, 30 extending mutually perpendicularly to one another, and each having an outwardly tapering end section 32, 34 respectively, for reception in the open end of the hollow flange member 10, inwardly of the planar side wall 20. At the other ends of their transverse portions 18, each hollow flange member is provided with a short hollow rearwardly extending part 36. The outer edges of corner pieces 26 are provided with rearwardly extending flanges 38, which on assembly are received within the rearwardly extending part 36 of the hollow flange member 10. The flange 38 extends around the centre corner section 40 of the corner piece 26, and around the outer edge of each limb 28, 30 thereof, being provided with a cut-away part 39 at the corner. Step formations 41, 42 are provided on the flange 38 along each limb 28, 30 dividing the flange into narrow outer and broader inner sections. On assembly, the step formations 41, 42 engage against the edges of rearwardly extending part 36 of the hollow flange member 10 to form a continuous line with the outer edge of extending part 36 to allow for uniform contact of both components with a drive/snap connecting cleat 60 described below.

The corner section 40 of the corner piece 26 has a first laterally offset portion 44 at its inner corner section, and a second laterally offset portion 46 at its outer corner section (FIG. 2). The first offset portion 44 protrudes radially inwardly from the corner of the section 40, and is offset in the direction of extent of the flange 38, an amount which is approximately equal to a single metal thickness of the hollow flange member 10. The edges of the first offset portion 44 form stops and engage against the ends of the hollow flange member 10, on assembly therewith. The second offset portion 46 is laterally offset in the opposite direction, to the same approximate extent. This second offset portion 46 terminates at each end approximately alongside the step formations 41, 42. Thus, when the corner piece 26 is assembled in flange member 10, a smooth outer side wall surface is formed between outer side wall 20 of the flange member and the outer side of the offset portion 46. This provides a smooth seating face, all the way around the corner of the assembled joint, for reception of the outer part of sealing gasket 17 as previously described. The first offset portion 44 in the assembled joint, and the protruberance 22, allows the end edge 24 of the duct side walls 12, at the corners thereof, to protrude into the gap between the duct sections, beyond the surfaces defined by the corner piece 26 at that location. This is as shown in FIG. 4. The end edges can, therefore, protrude to bite into the gasket 17 at this corner location, to complete the corner sealing of duct connection means in a simple but highly efficient manner, in accordance with the present invention.

A bolt hole 48 is provided, extending through the corner piece 26, through the second laterally offset portion 46 thereof. The periphery of the bolt hole 48 is square, so as to receive therein and hold against retention a bolt 50 having a head 52, square section shoulder 54, unthreaded portion 56 and threaded portion 58. In the assembly, the outer side faces of the corner pieces 26 are separated from one another, a distance of two metal thicknesses corresponding to the thickness of the two face-to-face abutting protuberances 22. The bolt therefore has an unthreaded portion which corresponds in length to the separation between the two corner pieces 26 and the thickness of the second corner piece. The square section portion of the bolt is of approximately the same length as the thickness of the bolt hole 48. Thus, in the assembly, bolts can be passed through adjacent corner pieces and bolted together by means of nuts, but the nuts cannot be over-tightened to cause bending of the corner pieces towards one another, and consequent distortion of the corner pieces and the hollow flange members, with the risk of spoiling the seal, is avoided.

This assembly is in some circumstances completed by the provision of cleats 60, of channel section but having lower inwardly extending gripping edges 62, 64. The cleats are adapted to be received over and grip the rearwardly extending outer parts 36 of adjacent hollow flange members 10 and rearwardly extending flange 38 of corner pieces 26 to hold the connection means together, as an alternative to or in addition to the bolts 50. Where the location of installation of the assembly permits, the cleats 60 may be clipped over the parts 36 from the outer side as indicated in FIG. 3. In circumstances where access to the outer side of a duct is not provided, e.g. when the duct is alongside a ceiling, the cleat 60 may be applied from one end of a pair of corners 26, as shown in FIG. 5. The cleat 60 is applied after the corner pieces 26 and flange members 10 have been assembled. The provision of cutaway part 39 at the outer corner in the flange 38 of corner piece 26 permits the cleat 60 to be installed from one end of the flange members 10, and forcibly driven along the length of the adjacent flange members 10 to the correct location. The length of the cleat in this case is such that it contacts the corners 26 on either end of the duct 14. In this way, the need for installation of bolt 58 at the far corner, which may be totally inaccessible, is avoided.

Fluid flow duct systems of the type described are subject to radially outward deflections, due to the air pressures in the duct when air is flowing therethrough. This can cause bending outwardly at the duct section joint, and spoil the effectiveness at the seal of such joints. In the present invention, this deflection tendency may be counteracted by inserting into the hollow flange members 10 a strip of reinforcing steel, of a thickness corresponding to that of the aperture through the hollow flange members, and a length suitable to extend from corner piece to corner piece, within the hollow flange members. Such reinforcing stiffness limit the amount of deflection, so as to prevent undesirable contact with proximate structures at the location of installation, where desired.

Thus the connection means according to the invention provides a simple and efficient duct jointing and sealing arrangement, which is easy to install. It can be used on a wide variety of duct systems, and can be installed by unskilled workmen, rapidly and efficiently.

It will be appreciated that the specific embodiment illustrated and described herein in detail is by way of example only and is not to be construed as limiting. The scope of the present invention is defined only by the appended claims. 

I claim:
 1. A connection means for connecting adjacent ends of rectangular sheet metal ducts, comprising:a plurality of elongated hollow flange members each having a channel portion with a mouth opening to receive therein an end face of a wall of said sheet metal duct and to extend along a major part of the length thereof, and a transverse hollow portion upstanding from the channel portion, said transverse portion having a generally planar upstanding outer side face; the channel portion extending beyond the plane of said outer face; the transverse portion having openings at each longitudinal end thereof; a substantially planar, generally L-shaped corner connecting piece, having co-planar limbs, said limbs being adapted to be received in the openings in the longitudinal ends of adjacent ones of said hollow flange members so as to link a pair of flange members together in mutually right angular disposed relationship with said planar outer side faces substantially in a common plane; said corner connecting piece having a first laterally offset portion at its radially inner central corner section and a second laterally offset portion at its radially outer central corner section, the first and second offset portions being offset in opposite directions from one another; said corner connecting piece being adapted to be assembled with a pair of said flange members with said first laterally offset portion being offset in the direction away from the planar outer side faces thereof; a gasket adapted to be placed in sealing engagement with the planar upstanding outer side faces of an adjacent pair of said flange members; the channel portions of said profile members extending beyond the plane of said outer face so as to form protuberances extending toward each other in the assembled joint, to grip the gasket in tight sealing engagement between opposed pairs of said flange members; each of the first and second offset portions of the corner connecting piece being offset from the main plane thereof sufficiently to protrude a distance of about one wall thickness of the flange member said first offset portion thus constituting means permitting end faces of said walls of the duct in the region of said first offset to project beyond the plane of said first offset portion towards said outer side face to grip said gasket in sealing engagement between opposed such regions of said end faces of opposed ducts.
 2. The connection of means of claim 1 wherein the corner connecting piece includes a flange along its outer edge, extending in the direction of offset of the first said offset portion said flange constituting means resisting flexing of said corner connecting piece.
 3. The connection means of claim 2 wherein the flange has a narrow cut-away portion at the corner thereof, to allow mounting of a slidable cleat assembly thereon.
 4. The connection means of claim 3 further including a cleat of generally channel shaped cross-section, adapted to be mounted over adjacent pairs of said flange members to assist in securing the assembly of the connection means.
 5. The connection means of claim 4 wherein the corner connecting piece includes a bolt hole near the corner thereof, extending through said second offset portion, for attachment to another similar corner connecting piece associated with the end adjacent sheet metal duct.
 6. The connection means of claim 5 wherein the bolt hole has a non-circular periphery, to engage against and prevent rotation of a bolt passing therethrough, and further including a bolt to pass through the aligned bolt holes of an adjacent pair of said corner connecting pieces, said bolt having a shoulder complementarily shaped to engage the periphery of one of said bolt holes and having a non-threaded shank portion adjacent to the shoulder thereof, of a length to correspond with the sum of the separation between said adjacent pair of corner pieces and the thickness of one of said corner connecting pieces, so as to guard against overtightening of a nut on said bolt. 